Field of the Invention
The present invention relates to a molding method and mold and in particular to a method of and mold for producing an elongated molding comprising a core and an outer layer, which is mounted on the opposite sides of an automobile such as along the middle of the doors.
Description of Related Art
An elongated double layered molding comprising a core and an outer layer surrounding the core has heretofore been produced by the sandwich molding method. In this method, a mold is used so that the core extends to the vicinity of the sides of the molding. The mold as shown in FIG. 23 includes a fixed mold half 30 and a movable mold half 22, and a molding forming cavity 23 is formed between the mold halves 30 and 22. A disposal tab forming cavity 25 is communicated with one end of the cavity 23 (right side as viewed in the drawing) via an orifice 24. The section of the orifice passage 24 which is normal to the longitudinal direction of the molding (horizontal direction as viewed in FIG. 23) is elongated and rectangular in shape as shown in FIG. 24.
In order to produce a molding by using such a mold, a molten resin for forming an outer layer 26 is injected into the cavity 23 from one end (not shown in FIG. 22) of the cavity 23 and then a molten resin for forming the core 27 is injected into the, cavity 23. After these molten resins reach the opposite end of the cavity 23, some of the resins are introduced into the disposal tab forming cavity 25 via the orifice passage 24. A molding in which the core 27 extends to the vicinity of the sides of the mold can be obtained.
However, whenever a molding having a semi-cylindrical section including a thicker central portion and thinner side positions is molded, the molten resin for forming the core 27 mainly flows along the thick central portion of the cavity 23 and reaches the orifice passage 24. The orifice passage 24 is rectangular in section and the characteristics of the resin are substantially uniform over the entire section. Accordingly, the molten resin for forming the core 27 easily flows through the central portion as viewed in the width direction of the orifice 24 while the resin hardly flows along the periphery or side portions of the cavity 25. As a result of this, the obtained molding includes the core 27 which is tapered toward one end of the molding. Properties such as rigidity and shape retention provided by the core 27 can not be sufficiently exhibited at the end of the molding.